The long term goals of this project are to arrive at a better understanding of how the central nervous system works to organize and control the limb movements involving more than one joint. The problems that arise in the organization and control of such movements concern questions such as: how is a point in space mapped into a proper set of joint angles so that the limb moves accurately to a target, how are the many muscles required to produce a movement coordinated, and what kind of feedback is appropriate to control multi-joint limb movements? This proposal deals with the last problem. Torques will be applied at the upper arm or forearm of human subjects and reflex electromyographic activity will be recorded. Results of these experiments should provide a better understanding of how the CNS normally controls movements, and provide the basis for a better assessment of movement disorders and for the design of prosthetic devices.